The present invention relates to circuits for sensor-controlled telemetry, and in particular to such a circuit utilizing opto-electronic image sensors for generating charge for production of corresponding digitalized information.
A circuit is known from the German patent application Pat. No. 28 38 647.2 wherein two linear image sensors each having a plurality of sensor elements have a corresponding number of evaluators post-connected to the sensor elements which undertake a digitalization of the sensor signals generated by radiation incident on the sensor elements. The evaluators consist of partial circuits of individual stages of a shift register which undertakes relative position displacements of the sensor signals in the longitudinal direction of the image sensors. The digital evaluation of the sensor signals is undertaken by means of a magnitude comparison of the sensor signals with a reference voltage with which all evaluators are supplied. The result of the magnitude comparison appears at the output of each evaluator in the form of a logical 1 or a logical 0. Thus, the luminosity data which is derived via the sensor elements from each of the two projected line sections from each image sensor is expressed by a plurality of logic signals available at the evaluator outputs which are in turn transmitted to a processing circuit for correlation measurement. In the processing circuit, that position displacement of the logic signals derived from one image sensor with respect to the logic signals derived from the other image sensor at which maximum correlation between the signals occurs is determined.
In circuits of the type described above wherein two linear image sensors are utilized, the image sensors may be matched as close as possible however the sensors will still exhibit differing sensitivities as a result of slight variations in material composition, or the reference voltages allocated to the evaluators may be slightly different for each image sensor or may even vary within one of the image sensors. Any variation such as these results in inaccurate logical data which in turn negatively influences the determination of the maximum correlation in the processing part. Accurate correlation is crucial to precise telemetry or focusing of the object on an image plane so that such variations significantly affect the overall accuracy of the entire device.